2.74

2.74 Describe the role of ADH in regulating water content of the blood

The amount of water in your urine is controlled by a hormone called antidiuretic hormone (ADH); this is made by a gland in hypothalamus. It flows through the bloodstream and targets the kidney (collecting duct). ADH allows more water to come out of the collecting duct by making the walls more porous. The effect is to control and alter the composition or quantity of water in blood. ADH has the ability to make the blood more or less concentrated (tissue fluids must be isotonic with the cytoplasm of the cell).

Collecting duct is responsible for selective reabsorption of water and this is affected by the amount of ADH in the blood. The consequence of ADH secretion is more concentrated urine and lower volume.

When it is hot, more water would be lost as sweat so more ADH would be produced. When it is cold, less water would be lost so less ADH would be produced. When one is dehydrated, they want to keep the water in the body so more ADH would be produced. 


ADH makes the collecting duct more porous allowing more water to be reabsorbed into the bloodstream.